Stethoscope bushing



April 7, 1 D. LITTMANN 3,504,760

STETHOSCOPE BUSHING Filed March 4, 1968 1 3 Sheets-Sheet 1 I NVE N TOR. DAV/0 A fimM/v/v Arrow/5X5 April 7, 1970 D. LITTMANN STETHOSCOPE BUSHING Filed March 4, 1968 United States Patent 3,504,760 STETHOSCOPE BUSHING David Littmann, Needham, Mass., assignor to Minnesota Mining and Manufacturing Company, St. Paul, Minn., a corporation of Delaware Filed Mar. 4, 1968, Ser. No. 709,993 Int. Cl. A61b 7/02 US. Cl. 181-24 11 Claims ABSTRACT OF THE DISCLOSURE A stethoscope bushing is shown wherein the bushing includes improved means for rigidly connecting ear tubes to a leaf spring contained within a Y-shaped sound tube of the stethoscope.

conventionally, stethoscopes have a pair of rigid ear tubes connected to the arms of a flexible, hollow, Y-shaped sound tube, the stem of the Y-tube being connected to the head of the stethoscope. In one construction, the ear tubes are tensioned toward each other by means of an external spring member, the ends of the spring member being attached to the exposed portions of the ear tubes. This construction has proven to be cumbersome and bulky.

Modifications of this design have incorporated the tensioning spring member within the Y-tube. Such constructions are shown in US. Patent Nos. 1,585,407 and 3,168,- 160.

The single spring member illustrated in Patent No. 1,585,407 has a short useful life, being incapable of withstanding continued flexing of the ear tubes because of the weakness inherent in the junction between the flat central section and curved end sections of the spring member. Patent No. 3,168,160 sought to overcome the inherent weakness of the junction between curved and flat portions of the leaf spring member by providing flat leaf spring means which were connected to the ear tubes by hollow, tubular bushings or helices, the ends of the ear tubes being held in rigid engagement to the ends of the flat leaf spring means.

However, the circular cross-sections of the bushings of Patent No. 3,168,160 limited the maximum width of the leaf spring means. Certain physical characteristics of the spring were limited, such as the obtainable spring force and the resistance to failure due to repeated flexure of the springs. Further, because of the curved nature of the inner surface of the bushings, only very small areas of contact were permitted between this inner surface and the end portions of the leaf spring means.

The present invention overcomes the inherent weakness of these prior art ear tube tensioning devices by providing the use of wider and therefore stronger leaf springs of substantially the same or greater thickness.

Further, the present invention overcomes certain limitations of stethoscopes by providing an improved bushing having an inner surface adapted to engage an end portion of the leaf spring means in surface-to-surface contact.

Briefly, the present invention provides a stethoscope having a pair of ear tubes and a flexible Y-shaped sound tube. The ear tubes are inserted into and extend outwardly from the arms of the Y-tube. The stem of the Y-tube is connected to the head of the stethoscope. A leaf spring means, comprising at least on leaf spring, is positioned within the arms of the Y-tube. The end portions of the leaf spring means extend into the arms of the Y-tube and engage the respective end portions of the ear tubes. The end portions of the leaf spring means are secured to respective end portions of the ear tubes by uniquely shaped bushings which enclose the junctions formed thereby. A portion of the inner surface of each bushing is contoured to engage in surface contact the respective adjacent end portion of the leaf spring means. Thus, wider or thicker leaf spring means of various cross-sectional configurations may be used. Further, greater surface areas of contact are provided between the bushing and the end portions of leaf spring means which are secured by the bushings to the ear tube end portions.

These and other objects and advantages of the present invention can be determined by reference to the accompanying description and drawing wherein:

FIGURE 1 is a fragmentary enlarged view, partially in cross-section, showing the structural relationship of a prior art bushing;

FIGURE 2 is an enlarged cross-sectional view taken along line 2-2 of FIGURE 1;

FIGURE 3 is an elevational view of a stethoscope using the improved bushing of this invention showing a Y-tube in cross-section with the lower portion of the Y-tube, normally connected to a stethoscope head, broken away;

FIGURE 4 is an exploded fragmentary perspective view of an end portion of an ear tube and the end portions of a pair of leaf springs of a stethoscope of the type shown in FIGURE 3 which are to be secured by the improved bushing of the present invention;

FIGURE 5 is a fragmentary enlarged view, partially in cross-section, showing the structural relationship between a partially milled-out end portion of an ear tube having dog ears and the ends of two flat leaf springs secured together by the crimped bushing;

FIGURE 6 is an enlarged perspective view of an uncrimped bushing used in FIGURE 5;

FIGURE 7 is an enlarged cross-sectional view taken along line 77 of FIGURE 5;

FIGURE 8 is an enlarged perspective view of another embodiment of a bushing using the teachings of the present invention; and

FIGURE 9 is an enlarged cross-sectional view of a sthetoscope using the bushing of FIGURE 8 and a pair of curved leaf springs, showing in cross-section the structural relationships between the inner surface of the bushing, the surfaces of the curved leaf spring end portions, and the surfaces of the milled-out ear tube end portion.

FIGURES 1 and 2 illustrate junctions formed between ear tube and leaf spring ends astaught by prior art, i.e. US. Patent No. 3,168,160. Referring to FIGURE 1, car tube end portion 10 is milled-out partially along its length to form a semi-cylindrical wall against which leaf springs 12 and 13 are secured by means of a bushing 14. The inner surface of bushing 4 as shown in FIGURE 2 is circular in rcoss-section throughout its entire length, thereby greatly limiting the widths of leaf springs 12 and 13 and permitting only line contacts 15 to be made between the edges of the leaf spring end portions and the curved inner surface of the bushing 14. In contrast, the present invention permits the use of leaf springs of any desired surface configuration and of increased widths, and further permits surface-to-surface contact between the end portions of the leaf spring means and the inner surface of the bushing.

A preferred embodiment of the present invention is illustrated in FIGURES 3-7 of the drawing.

Referring now to FIGURE 3, a pair of conventional stethoscope ear tubes 21 and 22 are provided with ear plugs 23 and 24 respectively at their outer ends. The other ends 25 and 26 of the ear tubes 21 and 22 extend into the respective arms 27 and 28 of Y-shaped sound tube 30, the stem 31 of the Y-tube being connected by suitable means to a stethoscope head (not shown). The Y-tube 30 preferably is made of flexible plastic material, for example polyvinyl chloride acetate.

End portions 25 and 26 of the ear tubes 21 and 22 may be identically formed as illustrated in FIGURE 4. A Section of an ear tube end section 26 is milled-out partially along its length to form a semicylindrical wall having opposed edges 34 and 35. In this embodiment a pair of dog ears 36 and 37 project from the opposed edges 34 and 35.

In FIGURE 4, a preferred embodiment using two flat leaf springs 40 and 41 formed of parallel strips of spring steel, preferably a grade of stainless steel, is shown. In other embodiments either a single or three or more leaf springs, which may or may not have a rectangular crosssection, can be used. The leaf springs may be of equal and uniform width throughout substantially their entire length, and are formed with slightly rounded longitudinal edges to avoid damage to the Y-tube. The leaf springs may be prestressed to form U-shaped arcs. In this embodiment, notches 43 and 44 are formed in the end portions of leaf spring 40 to engage dog ears 36 and 37 of the end portions of the ear tubes. It is contemplated that in other embodiments the dog ears and notches could be omitted entirely without departing from the teachings of this invention.

Referring now to FIGURE 5, a bushing 50 secures the leaf spring means in facing relation at its end portions to the opposed edges 34 and 35 of the semicylindrical end sections of the related ear tubes, dog ears 36 and 37 engaging notches 43 and 44. The junctions between the ends of the ear tubes and the ends of the leaf spring means are thereby enclosed and secured by the bushings. In this embodiment, the end 38 of an ear tube is illustrated as being beveled.

The bushings each are formed with an inner surface, one portion of which surface is contoured to engage, in surface contact, an end portion of the leaf spring means. In this manner, leaf springs of greater width may be used. Also, a greater area of contact may be provided between the end of the leaf spring means and the inner surface of the bushing.

FIGURE 6 is a perspective view of a preferred embodiment of a bushing 50 having an inner surface generally designated as 52. A portion 53 of inner surface 52 is substantially flat and is adapted to engage flat surface 45 (FIGURE 4) of an end portion of the leaf spring means. An annular surface 54 which forms another portion of the inner bushing surface 52 contacts the curved surface 39 of the ear tube end section illustrated in FIG- URE 4. Inner surface portion 53 of the bushing 50 preferably extends for more than half the length of the bushing and may extend the entire length thereof.

Referring to FIGURE 7, the flat portion 53 of bushing inner surface -2 engages the flat leaf spring surface 45. Other inner surfaces 55 and 56 of bushing inner surface 52 restrain lateral movement of the leaf spring means relative to the ear tubes. Leaf spring 40 is thereby held in contact at its end portion by bushing 50 and is secured to the opposed edges 34 and 35 of the ear tube end portion. The end portion of leaf spring 41 slideably engages the end portion of leaf spring 40 and flat surface 53 of bushing 50 while being held in position by bushing 50. In this manner, leaf spring 41 can slide longitudinally relative to leaf spring 40 and bushing 50 when the ear tubes are flexed with respect to eac hother. If desired, leaf springs 40 and 41 may be spaced apart at their centers, as illustrated at 42 in FIGURE 3.

The bushing 50 normally extends beyond the milledout section of the ear tube nearest the main ear tube portion, and the bushing 50' terminates at its other end short of the end 38 of the ear tube. Preferably, the heights of dog-ears 36 and 37 are equal to the thickness of leaf spring 40. The dog ears 36 and 37 coact with the bushing 40 to lock leaf spring 40 to the ear tube end portion 25, dog cars 36 and 37 engaging notches 43 and 44 of leaf spring 40. The milled-out portion of the ear tube preferably provides an end Wall 60 having a height at least equal to the thickness of the leaf spring means. The bushing 50 may be secured to the assembled ear tube and leaf spring end portions by crimping. When crimping the bushing 50 in place, various crimping means and patterns may be used such as dimples (shown at 57 and 58 in FIGURE 5), slots and corrugations.

Another embodiment of the present invention is illustrated by FIGURES 8 and 9. The ends of leaf springs 71 and 72 have curved or arcuate shaped cross-sections but otherwise are for-med and prestressed as described above. A portion 73 of the inner surface of bushing is contoured to engage the surface of the end portion of leaf spring 71 in sliding contact. The end portion of leaf spring 72 as formed with notches therein to engage dog ears formed on the opposing edges of an ear tube end portion, which is milled-out as described above. Inner surface portion 74 of the bushing 70 contacts the curved outer surface 76 of the ear tube end portion. Inner surface portion 73 of bushing 70 preferably extends more than half the length of the bushing and may extend the entire length thereof. When assembled, the bushing 70 may be crimped in place to secure the end portion of leaf spring 72 rigidly to the end portion of the ear tube.

Although several embodiments of the present invention have been described, any modifications, improvements or equivalents thereof are deemed to be within the scope of the invention.

What is claimed is:

1. In a stethoscope construction having a pair of elongated ear tubes and a flexible Y-tube with integral arms and a stem, each of said arms being adapted to receive an end section of one of said ear tubes, an elongated leaf spring means prestressed to form an arc and positioned within said Y-tube, the end portions of said leaf spring means extending into respective arms of said Y tube to engage corresponding end portions of said ear tubes, and securing means interengaging said end portions of said leaf spring means with said corresponding end portions of said ear tubes, said securing means comprising at least one bushing provided with an inner surface wherein a portion of said inner surface is contoured to and engages in surface contact an adjacent surface of at least one of said end portions of said leaf spring means to secure said at least one end portion of said leaf spring means to its corresponding ear tube end portion.

2. A construction acording to claim 1 wherein said elongated leaf spring means includes at least one elongated leaf spring and further comprises a pair of said at least one bushing for securing each of said leaf spring end portions to said end portions of corresponding ear tubes.

3. A construction according to claim 2 wherein end portions of at least one leaf spring are substantially rectangular in cross-section and have a flat surface forming a width dimension of said rectangular cross-section which is substantially greater than a surface forming the thickness dimension of said rectangular cross-section, and

wherein said portion of each bushing inner surface is substantially flat to engage said flat surface forming said width dimension of one of said end portions of said at least one leaf spring.

4. A construction according to claim 3 wherein the cross-sectional configurations of the ends of the bushing inner surface are D shaped and O-shaped respect vely.

5. A construction according to claim 4 wherein said one end portion of each of said ear tubes is formed with a semi-cylindrical wall having opposed longitudinally extending edges, said edges having dog ears formed therein, and

wherein each end portion of at least one elongated leaf spring is formed with notches therein,

said notches engaging said dog ears and said end portions of at least one elongated leaf spring lying against said opposed edges, and

said bushing is crimped about the junctions of said end portions of said leaf spring means and said nd p01... tions of said ear tubes.

6. A construction according to claim 2 wherein said one end portion of each of said ear tubes is formed with a semi-cylindrical wall having opposed longitudinally extending edges, and wherein said bushings are crimped to urge said edges in a tight relationship against said end portions of said at least one elongated leaf spring.

7. A construction according to claim 6 wherein said edges of said semicylindrical wall are formed with dog ears and each end portion of at least one of said elongated leaf springs is formed with. notches therein adapted to engage said dog ears, said crimped bushing securing said dog ears within said notches to restrain longitudinal movement of said end portion of the at least one elongated leaf spring relative to said end portion of said ear tube while maintaining said edges in said tight relationship against said ear tube end portions.

8. In a stethoscope construction having a pair of elongated ear tubes and a flexible Y-tube with integral arms and a stern, each of said arms being adapted to receive an end section of one of said ear tubes,

an elongated leaf spring means comprising a pair of elongated leaf springs prestressed to form U-shaped arcs and positioned within said Y-tube, the end portions of said leaf spring means extending into respective arms of said Y-tube to engage corresponding end portions of said ear tubes, said elongated leaf springs being positioned in facing relation at their ends and in spacing relation at their center portions and being of substantially equal and uniform Width along their entire length, one of said elongated leaf spring being longitudinally slideable with respect to the other, and

securing means interengaging said end portions of said leaf spring means with said corresponding end portions of said ear tubes, said securing means comprismg a pair of bushings each having an inner surface wherein a portion of each of said bushing inner surfaces is contoured to and engages a surface of one of said end portions of said leaf spring means to secure said end portion of said leaf spring means to said corresponding end portion of one of said ear tubes, said bushings being crimped to said ear tube end portions.

9. A construction according to claim 8 wherein the end portions of each of said pair of leaf springs are substantially rectangular in cross-section, the width dimension of each of said end portions being greater than the thickness dimension thereof, said Width dimension defining substantially fiat opposed surfaces, and wherein said inner surface portion of each of said bushings is substantially flat to engage one of said substantially fiat surfaces of an adjacent leaf spring end portion.

10. A construction according to claim 9 wherein said one end portion of each ear tube is milled-out to form a semicylindrical wall having opposed longitudinally extending coplanar edges,

said coplanar edges being urged by one of said bushings into tight facing relationship with one of said substantially flat leaf spring end portion surfaces,

wherein the inner surface cross-section of each of said bushings is D-shaped at one end of said bushing and O-shaped at the other end thereof.

11. A construction according to claim 10 wherein said coplanar edges of said semicylindrical wall are formed with dog ears and each end portion of at least one of said pair of elongated leaf springs is formed with notches, said dog ears engaging said notches and said coplanar edges engaging in tight facing relat onship adjacent areas of said substantially flat surfaces of said leaf spring end portions, wherein a portion of said bushing inner surface is contoured to engage in surface contact the rounded outer surface of said semicylindrical wall.

References Cited UNITED STATES PATENTS 3,168,160 2/1965 Littmann et a1 181-24 STEPHEN J. TOMSKY, Primary Examiner 

